Field
Exemplary embodiments of the inventive concept relate to a flexible display device, and more particularly, to a flexible display device including a capacitive type external touch panel.
Discussion of the Background
A touch panel disposed on a display device provides a touch sensing function that facilitates interaction with a user. The touch sensing function extracts contact information, such as sensing a touch or location of a touched surface when a user approaches or contacts the surface of the display device with the user's finger or a touch pen. The display device may receive image signals based on the contact information to display corresponding images.
The capacitive touch panel may include a sensing capacitor having sensing electrodes. The capacitive touch panel may determine whether a touch was made and a location of a touched surface by sensing a change in electrostatic capacitance of the sensing capacitor that is generated when a conductor, such as a finger of the user, approaches the touch panel. The sensing electrodes may be formed of a transparent conductive layer such as indium tin oxide (ITO), and patterned on a transparent substrate.
The development of the flexible display device requires providing flexibility to the touch panel. Accordingly, a touch panel including a substrate formed of a transparent plastic film has been developed. However, transparent conductive layer used as the sensing electrodes may have high light transmittance and high electrical conductivity but low flexibility. In other words, while transparent conductive layer may be thin, it may maintain a brittle characteristic.
Silver nanowire (AgNW), carbon nanotubes (CNT), or graphene may be considered as an electrode material for replacing the transparent conductive layer of the touch panel, but these materials may have a low optical characteristic (low light transmittance). Meanwhile, a technique of pre-forming a curved substrate of the touch panel and then adhering the sensing electrode to the curved surface of the substrate may also be considered. However, it may be difficult to pattern the sensing electrode to the curved surface of the substrate.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the inventive concept, and, therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.